Astronomers are predicting that the Earth might get hit by a chunk of space rock the day before, one large enough to wipe out life on the planet.

They have plotted the course of a one-kilometre-wide asteroid and found that it could collide with Earth on March 16, 2880, according to calculations reported today in the journal Science.

The research team at the Jet Propulsion Laboratory in Pasadena, Calif., is already proposing evasive action.

"It's a matter of not being taken by surprise," said Jon Giorgini, an engineer who heads the radar astronomy group at JPL, a division of the National Aeronautics and Space Administration.

Without knowing this asteroid was on a collision course, "all we would see is a flash and in a few minutes it would be game over," Mr. Giorgini said.

A similar collision with an object from space 65 million years ago may have led to the demise of the dinosaurs, Mr. Giorgini said. "The dinosaurs didn't see it coming; they didn't know their math and physics."

But he said Earthlings eight centuries from now should have little to fear. To begin with, there are enough factors that can change the way the asteroid moves to make the chance of a direct hit less than one in 300.

There is also plenty of time to plan a strategy to head off a collision.

"The beauty of this is we don't have to do anything about it now. We can spend a century just thinking about it," Mr. Giorgini said. "In that time, who knows what innovative solutions we can develop?"

The scientists tracked the asteroid with large radar arrays, hoping to prove how accurately the equipment could follow future movements of nearly 400 asteroids that have orbits bringing them near Earth.

It was a shock to discover a possible date for doomsday, Mr. Giorgini said.

He said more precise study is needed on how the asteroid spins and wobbles and how much light it reflects, factors that could alter its orbit.

The asteroid is known as 1950 DA, after the year of its discovery. It made another pass near Earth on New Year's Eve, 2000.

The next time it is due to approach Earth is in 2032. If techniques are not developed by then to precisely measure its distance from Earth, Mr. Giorgini suggested a space mission to the asteroid might be necessary.

Last year an unmanned space probe landed on the asteroid Eros.

Scientists have already begun working on ways to head off a collision.

One theory presented in the same issue of Science suggests that all that might be needed is to change the way an asteroid reflects light. Changes in what is known as the Yarkovsky effect can influence an asteroid's speed and orbit.

Joseph Spitale of the University of Arizona suggested that sending rockets into space to cover the outer layer of the asteroid with tonnes of dirt, or a covering that would reduce its reflectivity, could change its direction.

But that's by no means a sure bet. For one thing, Mr. Spitale estimated it could take at least 90 rocket loads of material to do the job. It would also have to be done 100 years or more in advance of the impact in order to generate an effect significant enough to do the job.

Many objects that might threaten Earth are discovered only a few months or years before they make a close encounter.

In fact, an asteroid that came nearly as close to the Earth as the moon on March 12 wasn't seen until it had already passed.

"It's not the asteroids we know about that we should worry about, it's the ones we don't know about that could give us a sucker punch," said David Balam, an astronomer at the University of Victoria.

An asteroid-watch program called Spaceguard Canada has been operating at the University of Victoria for the past 26 years.

The dinosaurs didn't see it coming; they didn't know their math and physics
this quote had my sides hurtin!

when march 15, 2880 comes and you all see the light and are finally ready to believe and come running over to my little space ship that's ready to leave the planet for a new home, i'm not gonna let on. it will just be me and me puppy oliver, travelling through the stars.

when march 15, 2880 comes and you all see the light and are finally ready to believe and come running over to my little space ship that's ready to leave the planet for a new home, i'm not gonna let on. it will just be me and me puppy oliver, travelling through the stars.

Originally posted by Lilly:.....unlessI canget in on that spaceship action...

alright. since you asked somewhat nicely we can take one less bag of ollie's food and you. we're gonna need someone as smart as you to terraform the new planet.
but you're gonna have to go with no luggage though. i simply don't have enough time to develop a bigger ship, now that plans are well under way.